Ok, I was doing Ulduar on my Lock and I thought "Damn, we need this"
"Azeroth has been broken, the works of the Pantheon in flame! The mortals attempt to cling to their civilization, but I have seen the rise and fall of civilization. Those cursed with flesh shall forever burn! The Pantheon, shall, fall!"
~Loken, Destroyer of Mortality
After the Halls of Stone and Lightning where destroyed, and Ulduar bested, the Horde and Alliance left the Ancient place. But as C'thun survived the armys of horde and alliance, so did Yogg-saron. He took control of Loken's dead body of stone, and created a massive floating citidel above Storm Peaks, (Three times the size of Dalaran) and named it Udael. With it, he gathered the remaining Iron Dwarves, Iron Vulkuri, and Mechagnomes and reforged even more armys. He moved the citidel away from Northrend, to above where Quel'danas once was (Just a random location I picked). He has rebuilt the ruins of Silvermoon into a new, darker baston of power. From there, he sends his armys to destroy all that would appose him.
Loken would be in the center of the Citidel, where a tall tower stands, controling the citidel. Should he leave the citidel, it will not move. Loken cannot be defeated inside of the tower, but if he travels outside then he can be killed. (I don't mean he would be invulnerable in the tower, just that he would continuesly revive). If he does die, he will drop an item, which if some other hero picks it up, he can travel to the tower and control the citidel. The Citidel has abilitys that help it control the tide of battle;
Fire Turret: At the edged of Udaer hold multipul turrets that will automaticly fire at nerby units.
(Can't think of any more none rigged ideas)
I understand that you are prolly filling on places for players, so don't be afraid to turn it down.